Chopped fiber glass strand is commonly formed by mechanically chopping a continuous glass fiber strand either from a forming package or directly as the strand is attenuated from a bushing. A typical process for chopping fiber glass strand wet in a forming operation is the process described in U.S. Pat. No. 3,869,268 assigned to the assignee of the present invention. In this process glass fibers are attenuated, treated with a binder or size and after being gathered into a strand, the strand is pulled between a roller having a rubber surface and a second roller having a plurality of cutting blades therein. The glass strand is then chopped between the two rollers as the filaments are being attenuated.
In another process for producing chopped strand the strands are fed to a chopping operation from a forming package. In this process the strand is in dry form. A typical operation of this latter type is shown in K. L. Lowehstein, The Manufacturing Technology of Continuous Glass Fibers, Elsevier Scientific Publishing Company (New York: 1973), Pages 266-267.
In U.S. Pat. No. 3,510,393 a continuous glass strand is disclosed which is unique in that it is composed of a multiplicity of glass filaments which have hollow configurations. The continuous strands formed and described in this patent have external diameters of 0.0003 to 0.003 inch (0.0076 to 0.076 millimeters) and 10 to 65 percent of their volume is hollow. These continuous strands because of their hollow configurations possess excellent dielectric properties and find utility in filament winding with various resins to form rocket motor cases, radar domes and the like. Unfortunately because of their hollow configuration and the nature of prior art processes for cutting glass fibers, the hollow fiber strands are used only in a continuous strand form. If these strands were cut by normal procedures, the hollow ends of the severed strand are kept exposed to the environment, thus rendering them unsuitable for reinforcing resin matrices where it is desired to take advantage of their highly specialized dielectric properties.